This second program is based on the first, but uses the Modbus Master protocol available in the latest release of the MicroLogix 1200, as well as a 1761-Net-AIC.
The biggest obstacle in getting this configuration to work was trying to find the polarity of the comm lines (i.e. does + comm on the AIC go to A or B comm on the drive?) as well as realizing all the modbus addresses are offset by 1 (which even Rockwell Drives Div. missed in Rev 1 of the subsequently release tech note).
Since this file was published, Rockwell has release (and fixed) a tech note, and also has an excellent 2004 HOT LAB.
- RSLogix 500 Version: 6.1
- Additional Requirements: Micro1200 & PowerFlex 4 /40
- File Size: 60 kb
- Uploaded on: 02/09/04
- Entered By: Shawn Michael Tierney
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Note: This article was previously posted on the author's original websites, www.ShawnMichael.com and www.ShawnMTierney.com
- Update: MicroLogix 1200 to PowerFlex 4 using Modbus is now available for a $1 donation to our website at:
I have a project with 5 powerflex 4m controlled by a micrologix PLC via modbus.
I am able to control and monitor the powerflex with no problem but would like to be able to monitor drive temperature, adjust ramp speeds and min max speeds as well.
Using info from the AB website and others, I have tried to read the info I want but have not been successful.
Hoping you can point me in the right direction. If you can get me started I think I can work everything out.
JAQGood afternoon ,
So you're using MicroLogix with the 4m and Modbus? Last time I ran into an issue doing this is was that the address was off by 1 as some modbus devices are 0 based, and some are 1 based.
Did you try the code in the PF4 book I mention in the article?
Automation Instructor at TheAutomationSchool.comI am aware of the address offset and have taken that into account. Figured that one out by trial and error a while back.
I am not able to access the article mentioned. I get a page referring to maintenance mode.
I have looked through the powerflex 4 and 4M manuals and think I am following the instructions correctly.
The good thing is the job is close and the project is an internal one for maintenance purposes for my own use.
Going to the site later this week or the first of next week to do some further testing on this issue.
JAQSo for anyone who comes across this thread, first let me say the article this thread is for is:
And the manuals my code is based on is linked below:
While TheAutomationExchange is down while I move it, you can still access the very same code inside the above mentioned manuals.
And having using this code dozens of times in the field, I can confirm it works.
The biggest mistakes I've seen people make is either (1) having your address off by 1 or (2) reversing your wiring.
PS - Here's a picture of my notes from my code - I put a lot of notes in there to help folks, but sometimes they just can't get it on their own and need to hire a programmer:
I should probably also mention this is from 2004 😉